Lithographic press with combined inking and water spray dampening



M y 11. 1954 w. w. DAVIDSON, JR 2,673,001

LITHOGRAPHIC PRESS WITH\COMBINED INKING AND WATER SPRAY DAMPENING FiledJan. 6, 1950 IN VEN TOR.

Patented May 11, 1954 UNITED STATES PATENT OFFICE LITHO GRAPHIC PRESSWITH COMBINED In lithographic offset printing a rubber blanket transferthe printing to the copy sheets from an inked plate, the ink-bearingportions of which must be repeatedly re-inked Without inking the clearportions. This is accomplished by keeping the clear portions damp. Thusthe plate is rolled first by one or more dampening rolls and then by oneor more inkin rolls.

Lithographic printing is an old art and for many years has beensimplified enough for use on office type presses. Nevertheless it stillrequires rather delicate adjustments with th result that unskilledoperators have much trouble. If a little too much Water or dampeningsolution is applied, the unskilled will notice that the prints arerunning light and will increase the supply of ink. In turn, this maycause an ink scum to start spreading over the plate, leading theunskilled operator to apply still more water, etc. Eventually this leadsto various other troubles, one being that the excess ink works back intothe water rollers and may permanently harm them.

Various attempts have been made to avoid this need for criticaladjustment and to simplify the operation of the press. An emulsifiedmixture of ink and. dampening fluid fed by one set of applicator rollshas been tried. It was a failure commercially because of the poorquality of the printing. A set of convergent branches, one for water andone for ink, with a common final applicator roll for the two branches,has simplified the structure but with a greater tendency for ink to workback through the water rolls.

According to the present invention, water is supplied directly orindirectly to the ink-applying form roll by spraying. In this way it ispossible to spread the water uniformly along the form roll and to mix orcoat the ink with it so that it does a perfect job of dampening theplate without any danger that the ink will work back into the watermechanism. The ink tends to refuse to accept much excess water, or anymore than can be disposed of by evaporation. The ink can carry excessWater back to other ink rolls where small excesses can evaporateharmlessly. Thus both the critical adjustment for the water supply andall danger of gumming up the water attachment with ink are avoided.

Water spray has been tried before but notwith these advantages. When thespray is applied directly to the plate, an excess must be applied toensure that every bit of the clear part of the plate i reached. Thegumming up of the water attachment is avoided; while the need forcritical adjustment remains. I 1

Other advantages and objects of the invention will be apparent from thefollowing description and the drawings.

General designation of figures Figure 1 is a diagrammatic viewrepresenting a longitudinal cross section of one form of the inventionchosen for illustration.

Figure 2 is a diagrammatic view representing the face view of thewater-applying device of Figure 1.

Figure 3 is a fragmentary diagrammatic view showing a modified form ofthe invention.

Figure 4 is a fragmentary diagrammatic face view of the structure seenin Figure 3 as viewed from the left.

General description Although the invention is useful with anylithographic type of machine, it has been illustrated as used with atwo-cylinder type of press commonly used as an office duplicator. Thusin the illustrated form, the press includes a large cylinder II and asmall cylinder I2. The large cylinder I I has a plate holding segment I3to which a plate I 4 bearing the matter to be printed is attached. Afterthe plate I4 is properly inked, it rolls against a rubber blanketcarried by cylinder I2 frequently called the blanket roll. A reverse inkimpression of the matter being printed is thus applied to the blanketroll. Thereafter a sheet of paper to be printed is fed by the feeder Itto pass between the cylinders in registration with the impression on theblanket so that the ink of this impression will be printed on the sheetat the desired position thereon. As the sheet passes through the bitebetween the cylinders it is backed up by a platen segment IT. Theprinted sheet is discharged to a catch box or discharge device i8. A amatter of practice, it may be turned over first by means not shown, sothat it will be deposited on a pile printed side up.

The ink is applied to plate I 4 by a series of inkin rolls, the first ofwhich, 2 I, is sometimes called the fountain roll and picks up ink froma supply held against it by an adjustable blade 22. The roll or rolls atthe end of the series of inking rolls and which bear against the plateI4 are called form rolls. In the illustrated form of the invention,there are two form rolls, 23 and 24. The present invention relates tothis inking assembly or attachment.

Although the law requires a full and exact description of at least oneform of the invention, such as that which follows, it is, of course, the

purpose of a patent to cover each new inventive concept therein nomatter how it may later be disguised by variations in form or additionsof further improvements, and the appended claims are intended toaccomplish this purpose by particularly pointing out the parts,improvements or combinations in which the inventive concepts are found.

Need for dampening In lithographic printing, it is necessary to dampenthe plate l4 and to maintain the inkfree portions of the plate thereofin a damp condition so that ink from the form rolls 23 and 24 will notstick to these ink-free portions. Thus the dampening of the plate givesit a selective affinity for the ink. Although the ink from the formrolls 23 and 24 will not adhere to the damp ink-free portions of theplate, it will adhere to and therefore will ink the image or printingportions of the plate.

Description of novel feature According to the Figure 1 form of thepresent invention, the dampening is accomplished by spraying water(dampening solution) onto the first form roll 23. This has been showndiagrammatically as accomplished by a spray tube 26 which extends alongthe length of form roll 23. The spray tube 26 should project a finelydivided spray of water uniformly along the length of the ink-applyingportion of form roll 23. To make the drawings more fully illustrative,this is represented diagrammatically in Figure 2. Thus the tube 28 isslotted on the side thereof facing roll 23 and a water spray is blowninto each end of the tube by an air nozzle 2? which blows a jet of airacross a water nipple 28. The jet of air draws water from the nipple 28and atomizes it so that it can easily carry the water into the tube 26and out through the slot 29 thereof against the entire length of theinking portion of form roll 23. The tube 26 may be longer, so thatnipples 28 lie within it, if desired.

The normal water level is maintained at a constant depth close enough tothe tip of nipples 28 so that the water will be drawn therefrom by theair jet. This may be accomplished by a conventional dampening fountainconstruction in which a container 3| of dampening solution is invertedinto a pan 3:: from which the solution runs through pipes 33 to thenipples 28. It may be noted that the conventional dampening solutionsare mainly water and the terms water" and dampening solution are usedinterchangeably.

Although the application of the spray to any point of the inking rollsis within the contemplation of this invention, it is at presentpreferred that the point of application be separated by at least onebite between inking rolls from the bite of the form roll with the plate.Thus in Figure l the water from the spray tube 28, after being appliedto the roll 23, passes through the bite between roll 23 and distributorroll 36 before it reaches the plate !4. In other words, although thespray tube 26 appears to be adjacent the plate I4, it is separated fromit operationally by the bite between form roll 23 and distributor roll36. The separation by such a bite is generally preferred because itspreads the dampening fluid out more uniformly.

After the inker assembly has been driven enough so that the variousrolls thereof are coated with ink, the spray will be started. If it isfound to take some time before enough water from the spray has workedinto the ink for successful printing, the form rolls 23 and 24 will,until then, be raised from the plate |4. According to a modified form ofthe invention, the tube 26 may be positioned, or may be shiftable to bepositioned, at the upper or left hand side of form roll 23 so as not tobe separated from the plate by a bite between ink rolls. This may bedesired for situations in which adequate dampening would otherwise notbe dependably obtained.

Applying the dampening spray to the ink rolls at any point thereofinstead of directly to the plate is a feature of this invention. It isbelieved that applying the spray directly to the plate would be verylikely to result in either inadequate dampening of some spots of theplate or excessive dampening of others, or at least in a tendency towardsuch unequal distribution which would make adjustment for satisfactoryprinting very difficult, especially for inexperienced operators.

A drip trough 31 is preferably provided below spray tube 26 to catch anywater which drips from it and to conduct it to a drain tube 38.

To ensure evaporation of excess dampening fluid which may work back toink rolls 39 or to second form roll 24, a blast of air (heated ifdesired) may be directed on them by a nozzle 49, or a plurality of suchnozzles.

Modification Another form of the invention has been shown in Figures 3and 4. In this form the inker roll to which the spray is applied is notone of the main train of rolls, but is an extra distributor roll 4|.This roll 4| has been shown running in contact with the form roll 23 onthe side of the latter approaching the plate |4. By rearranging parts itcould en age the form roll 23 elsewhere or it could engage one of theother inker rolls. The illustrated position is preferred because it willresult in relatively little dampening solution working its way from formroll 23 to distributor roll 36.

The illustrated arrangement of roll 4| and the roll with which itengages has another advantage. Spray tube 26 may be positioned belowroll 4| so that any excess water gathering on the surface of spray tube26 will run away from the slot 29 therein thus reducing the chance thatlarge drops of water will cause any difficulty. This danger is furtherreduced by virtue of the fact that if an excess of water is applied tothe roll 4| it will be carried around the roll and collected in trough42 between the roll 4| and form roll 23. Should the spray tube 26continue to apply an excess of water to roll 4|, the excess willaccumulate in trough 42 until it runs to the ends of the rolls and dripsinto drip pan 43. It will be observed that the inker rolls such as 23and 4| are commonly wider than the press roll so that it would be easyto catch the drippings from the ends of such rolls even if they were notpositioned to the side of roll II as seen in Figure 3. An air nozzle 45may be provided for blowing water from this trough as fast as itaccumulates. This feature may be used in other forms of the inventionwherever water tends to accumulate.

The second form roll 24 is relatively free from water and hence ensuresperfect inking for high quality printing. It may be understood thataccording to conventional practice the amount of ink fed may beregulated by adjusting blade 22 (Figure 1) and by varying the proportionof time that ductor roll 46 engages ink fountain roll 2|. All of therolls rotate constantly except fountain roll 2|, which is intermittentand preferably adjustable, and ductor roll 46, which is free.

From the foregoing it is seenthat a lithographic press has been devisedin which the correct supply of dampening solution to the plate is easilyaccomplished without any danger of gumming up the dampening mechanism soas to impair its function for supplying the dampening solution. Byapplying water spray to an inking roller, the danger of excessiveapplication of Water to the plate is virtually eliminated.

According to another aspect of the invention, water is applied to theinking assembly and is largely confined to the desired path of feed andto satisfactory concentrations by applying drying influences to inkrollers on which the water is not desired.

The amount of excess water which needs to be evaporated (with any typeof water supply feeding an excess) can be reduced by blowing away anywater that accumulates as droplets in troughs formed by the rolls. Thiswill often enable the excess to evaporate naturally. At present it ispreferred to avoid directing such an air blast along the the plate rollwhere it might objectionably dry the plate.

I claim:

1. A lithographic press including a plate holder, an ink-applying unitincluding a final ink form roll and supply and distribution meansincluding at least one preliminay roll engaging said form roll, an inkerbranch including an ink form roll engaged by the plate as it approachesthe final form roll and supplied with ink from said supply anddistribution means, a sprayer for applying a spray of aqueous inkrepellent to the inker branch whereby repellent is received by the formroll thereof predominantly over the final form roll,

1, in which the sprayer is positioned to applythe spray to the ink formroll of the branch at a portion thereof which is leaving the plateholder and is approaching a line of contact with a distribution rolleralong which ink moves in said branch toward said ink form rollerthereof.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,834,169 Moe Dec. 1, 1931 1,889,374 Renck Nov. 29, 19 22,103,254 Goedike Dec. 28, 1937 2,106,732 Goedike Feb. 1, 1938 2,127,955Frazier Aug. 23, 1938 2,264,523 Gustafsson et a1. Dec. 2, 1941 2,340,319Goedike Feb. 1, 1944 2,395,151 Sodomka Feb. 19, 1946 2,546,793 SodomkaMar. 2'7, 1951 FOREIGN PATENTS Number Country Date 502,316 Great BritainMar. 14, 19 9

